Prior art devices of this kind of which the inventor is aware, include those disclosed in the following U.S. Patents:
No. 5,671,865 which is the inventor's own patent PA0 No. 5,097,984 PA0 No. 5,067,627 PA0 No. 4,971,222 PA0 No. 4,805,801 PA0 No. 4,739,902 PA0 No. 4,674,635 PA0 No. 4,285,114 PA0 No. 4,269,324 PA0 No. 3,871,641 PA0 No. 3,124,268 PA0 No. 2,819,817 PA0 No. 2,478,815 PA0 No. 2,290,006 PA0 No. 1,719,451 PA0 No. 1,362,058 PA0 No. 416,340
The inventor is also aware of the device shown and described in Italian Patent No. 343,567. United States patents as well as foreign patents are available to those who are interested including the general public. Copies thereof can be obtained without difficulty.